TypeScript Strict Mode Type Errors in Next.js

1. Variables not properly typed, inferred as unknown or any
2. Null/undefined not handled, accessing properties on potentially null values
3. Function parameters not typed, defaulting to any
4. Event handlers missing proper event types
5. Using non-null assertion (!) instead of proper null checks

Type everything: Add explicit types to functions and variables: const name: string = 'John'; function greet(name: string): void

Handle null/undefined: Use optional chaining (?.) and nullish coalescing (??): user?.email ?? 'no email'

Event types: Import from React: const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {}

Gradual adoption: Enable strict mode incrementally. Start with tsconfig.json strictNullChecks: true first.